Several related experiments on cell membranes are planned. 1. Inside-out vesicles prepared from human red cells by the method of Kant and Steck have been shown to transport Na from the cytoplasmic face across the membrane by a ouabain inhibitable, ATP dependent process. We will use this preparation to study the effect of the enzymes of intermediary metabolism on ion transport. 2. Preliminary studies have indicated that the uptake of phloretin by egg lecithin vesicles can be studied by the Eigen temperature jump method on a 10 microsecond time scale. We will compare the kinetic parameters of this reaction in these vesicles with those in red cell lipid vesicles and red cell membrane vesicles. 3. We have determined delta G, delta H and delta S for the interaction of small nonelectrolytes and polypeptides with egg lecithin vesicles to characterize the thermodynamic parameters of these solute-membrane interactions in the presence of all the lipid components of red cells as well as red cell proteins. 4. We will use subnanosecond fluorescence spectroscopy to study the relaxation of polarized excitation of probe molecules to determine their rotational diffusion coefficients and thus obtain an estimate of the microviscosity of red cell membranes of man and dog. BIBLIOGRAPHIC REFERENCES: Ting, P. and A.K. Solomon, Temperature Dependence of N-Phenyl-1-Naphthylamine Binding in Egg Lecithin Vesicles. 1975. Biochim. Biophys. Acta 406:447-451. Solomon, A.K., Thermodynamic Aspects of Nonelectrolyte Permeation of Lipid Bilayers. Proceedings of the Study Week of the Pontifical Academy of Sciences, Vatican, April 1975. In press.